In large scale electronic circuit design such as that utilized for data processors, the implementation thereof in printed circuit board wiring generally requires several levels of prototype test and evaluation before finalization. During this period, the initially designed printed circuit boards often require modifications to permit changes in logic or additions of functions previously omitted. Since a sizeable number of different printed circuit boards may be involved, it is not practical to lay out and fabricate new boards for each change. Instead, some means must be provided to alter the interim printed wiring. This is generally accomplished by cutting appropriate printed leads to provide open circuits and reestablishing circuit paths by using external wires to connect portions of a board or to interconnect different boards.
Common methods of severing the printed leads on the circuit boards include a hand held razor blade type knife or an engraving type motor tool with a rotating or oscillating abrasive bit. The difficulty with these rather primitive methods is that the cutting operation is uncontrolled as to precise location or the depth of cut. Accordingly, adjacent printed wires which are closely spaced to those being severed in high density boards may be damaged, or in the case of multilayer boards, printed leads below the board surface may be inadvertently severed. Additionally, the use of these methods, even when carefully implemented by an operator, is tedious and time consuming.
It has also been observed that electrical faults sometimes lie below the board surface in multilayer boards. One such fault produced by metallic whiskers formed during the manufacturing process, causes short circuits to occur between the printed wiring and metallized via holes.
What is required is a hand held, simple, low cost tool that provides a method of controlled cutting of printed circuit leads or spurious conductive paths, with respect to location as well as depth within the board. The cutting tool of the present invention fills this need.